This invention relates generally to switching-type voltage regulators and more particularly, it relates to a buck regulator command charge circuit which includes a compensated-gain control circuit for compensating for changes in the component values in order to achieve optimum voltage regulation. In particular, the command charge circuit of the present invention has specific applications in systems which require a high degree of voltage regulation, such as laser systems, induction accelerator systems, radar systems, and power conditioning networks for copper laser oscillators.
As is generally known to those in the art, a voltage regulator is used to provide a predetermined and substantially constant output voltage from an unregulated input voltage. One such type of voltage regulator is sometimes referred to as a "buck regulator command charge circuit." The command charge circuit typically uses an insulated gate bipolar transistor (IGBT) as a switch to provide a pulsed flow of current to a network formed of inductive and capacitive energy storage elements which smooth the switched current pulses into a continuous and regulated output voltage. Thus, the IGBT is turned off and on appropriately so as to regulate the charge voltage on a primary capacitor of the modulator.
In operation, the conduction time of the IGBT (i.e., when the switch is closed) can be determined by calculating the instantaneous energy stored in the primary capacitor and the charging inductor. When the sum of these two energies are equal to the final desired energy to be stored in the capacitor, the IGBT is turned off (i.e., the switch is opened). Therefore, the values of the charging inductor and capacitor must be precisely known in order to achieve optimum voltage regulation. It is these values which determine the gain factor to be used in a control circuit within the buck regulator command charge circuit.
The prior art buck regulator command charge circuit 110 which includes a fixed-gain control circuit 112 is illustrated in FIG. 1 and has been labeled "Prior Art." It will be noted that when the charging inductor L.sub.c is required to be replaced or the buck regulator command charge circuit is to be operated with a different modulator, it will be necessary to adjust the gain of the fixed-gain control circuit 112 to match the new values for the primary capacitor C.sub.o and the charging inductor L.sub.c. Furthermore, the values of the components C.sub.o and L.sub.c can change due to aging, thermal, and non-linear effects. Accordingly, this prior art buck regulator command charge circuit has the drawback that it does not achieve optimum voltage regulation at all times.
In view of the foregoing, it would be desirable to be able to provide a buck regulator command charge circuit which does not suffer from poor output voltage regulation due to instability of the command charge components. The present invention represents a significant improvement over the prior art buck regulator command charge circuit illustrated in FIG. 1. The buck regulator command charge circuit of the present invention includes a compensated-gain control circuit for compensating for changes in the component values in order to achieve optimum voltage regulation.